It is important in human nutrition but deficiency is rarely observed in the absence of some complicating disease except in the infant during the first ten days after birth. Vitamin K is present in a large variety of foods and is synthetized by bacteria in the intestinal tract, hence dietary deficiency is an unlikely possibility. Deficiency in the first few days of life may be due to inadequate intake during this period or to sterility of the intestinal tract. The daily requirement of the infant is approximately 1.0 g. (4a). In the adult, the requirement is unknown but is apparently small and easily sup-plied by the ordinary diet in addition to the amount avail-able from intestinal synthesis.
Since naturally occurring forms of vitamin K are fat soluble, deficiency is observed in a number of diseases in which fat absorption is impaired, such as obstructive jaundice, biliary fistula, and the stcatorrheas: sprue, the celiac syndrome, idiopathic steatorrhea and pancreatic fibrosis. Poor absorption of vitamin K may lead to deficiency in chronic ulcerative colitis, regional ileitis, other severe diarrheal states and following operative removal or short circuiting of large sections of the intestinal tract. Intestinal synthesis of vitamin K may be depressed by prolonged administration of antibiotics.
Vitamin K is essential for the formation of prothrombin which is necessary for blood coagulation. The precise role of vitamin K in prothrombin formation by the liver is unknown; it has been postulated that it may function as the prosthetic group of an enzyme (158). Functions for vitamin K other than involvement in the synthesis of prothrombin have been suggested. In animal experiments, vascular and parenchymal lesions which could lead to hemorrhage or tissue injury have been found in the brain in vitamin K deficiency. Whether tissue lesions precede hemorrhage in infants deficient in vitamin K is unknown. It is of interest, however, that not a single instance of cerebral hemorrhage was noted in 1531 children in Oslo who were born of women who received vitamin K during the last weeks of pregnancy.
Vitamin K Deficiency
The outstanding manifestation of vitamin K deficiency is hemorrhage which may occur into any tissue or from any mucous membrane. Cerebral hemorrhage is frequent in infants deficient in vitamin K and has also occurred in adults. Diagnosis of vitamin K deficiency is dependent on estimation of prothrombin activity of blood. A number of procedures are available for this purpose, all of which consist of indirect estimation of prothrombin concentration.